This invention relates to a new clear solution of plant nutrients for direct application to the foliage of living plants. More particularly, it relates to the composition of and a method for the production of a new clear liquid solution of partially condensed urea and formaldehyde, substantially free of formic acid, which may be stored as a clear solution for extended periods of time under ordinary commercial fertilizer storage conditions, and which remain sufficiently reactive to allow its partially condensed urea-formaldehyde content to react further to produce slow-releasing or water-insoluble nitrogen when applied directly to the neutral or acid surfaces of living plants or soil.
Liquid fertilizers have been used in commercial agriculture for many years to obtain accuracy and convenience of application and the economics and ease of handling and storage. Recently, foliar feeding of plants has been demonstrated to be a method for providing plant nutrients with increased efficiency. Foliar feeding has been effective with grasses, legumes, fruit trees, vegetables, ornamental plants and many other types of plants.
The prior art contains numerous uses of condensed urea and formaldehyde to provide slow-releasing and water insoluble nitrogen nutrients for fertilization of living plants. These slow-releasing nitrogen fertilizers have usually been solid products which have relatively low nitrogen availabilities for use by the plants. That is, about one-half or more, of the water insoluble nitrogen never becomes available to the plants to which it is applied. Solid fertilizer products are not physically suitable for application directly to the foliage of living plants.
The prior art describes a process which will produce urea-formaldehyde concentrates, high in urea content, comprising aqueous suspensions which remain flowable mixtures for at least 30 days. Also described in the prior art is a process for producing a stable solution of urea and formaldehyde having a urea to formaldehyde ratio above 1 to 1 and containing up to 6% liquid or gaseous ammonia added to the heated urea formaldehyde reaction. These high urea formaldehyde suspensions and concentrates are primarily designed for further reaction under conditions of elevated temperature and strong acid catalysts to produce solid fertilizers, and secondarily to provide urea-formaldehyde based fertilizer solutions.
Urea-formaldehyde concentrate solutions containing substantial amounts of ammonia, while storage stable, are undesirable as foliar feeds, because free ammonia applied to the foliage of living plants causes burning and leaf damage which may actually kill the treated plant. Further, ammonia reacts with the ends of low molecular weight urea-formaldehyde compounds, causing them to become resistant to further condensation reaction. To achieve slow-releasing nitrogen on the foliage or soil surfaces, further condensation of highly active urea-formaldehyde compounds is required.
The art has recently provided products, and processes for producing them, which are aqueous suspensions of water insoluble organic polymers, including urea-formaldehyde polymers, which may be effectively applied to the foliage of plants to supply slow-releasing, water-insoluble plant food nitrogen. Although these materials are agronomically effective, the suspensions cause handling difficulties from sediment in storage tanks and clogging of pipes and valves. Pluggage of application nozzles and inaccurate distribution through these nozzles is a particularly bad problem with these suspensions.
Relatively large amounts of strongly basic materials, such as alkali hydroxides, have been used as catalysts in the prior art urea-formaldehyde preparation reactions at temperatures as high as 100.degree. C. or more. These drastic reaction conditions cause significant hydrolysis of formaldehyde to formic acid and formate salts. Formic acid and formate salts can cause severe foliage damage when applied directly to a plant and formic acid formation is a waste of formaldehyde raw material. Neutralization of excess formic acid with base material to provide storage stability of the concentrate creates a large buffer. This buffer can be large enough that it is not overcome on the surface of the treated foliage or soil and this further condensation of the urea-formaldehyde, which requires neutral or acid conditions, does not proceed at a speed needed to make the nitrogen slow-releasing.
There has been no disclosure of a storage-stable, clear liquid, partially condensed, urea-formaldehyde fertilizer solution which is sufficiently reactive to allow the urea-formaldehyde condensation to again commence to form slow-releasing and water-insoluble nitrogen when applied to the neutral or acid foliage of living plants or the soil, thereby effectively providing nitrogen which is released to the plant throughout an extended period of time without the hazard of damage to the plant.
It is a primary object of this invention to provide a clear, stable, and storable liquid solution of plant nutrients, substantially free of formic acid, comprising partially condensed urea, and formaldehyde, partially neutralized alkali hydroxides, and water, which may be safely and efficaciously applied directly to the foliage of living plants.
It is a further object of this invention to provide a clear aqueous solution for providing plant food nitrogen in a non-burning form directly to the foliage of living plants.
It is a further object to provide a clear aqueous solution of water soluble plant food nitrogen which forms water insoluble plant food nitrogen without further treatment when it is applied to the neutral or acid surfaces of plant foliage or soil.
It is a further object to provide a clear aqueous solution of water soluble plant food nitrogen which may be blended with other water soluble plant nutrients to form complete liquid fertilizers and form water insoluble plant food nitrogen when the mixed solution is applied to neutral or acid surfaces of plant foliage or the soil.
It is a further object to provide clear, stable, and storable liquid foliar fertilizer solution suitable for direct application to the foliage of living plants without the hazard of foliage damage.
It is a further object of this invention to provide a method for preparing a clear, stable, and storable solution which provides non-burning plant food nitrogen when applied directly to the foliage of living plants.
It is a further object to provide a method for preparing a clear, stable, storable solution of plant food nitrogen which forms water insoluble plant food nitrogen when applied to acid or neutral plant foliage or soil surfaces.
It is a further object to provide a method for preparing a clear, stable, and storable complete liquid fertilizer solution substantially free of formic acid and which forms water insoluble nitrogen without further treatment after application to the foliage of living plants.
It is a further object to provide an improved method for supplying water insoluble plant food to the foliage of grasses, and agricultural and ornamental plants, having acid or near-neutral surfaces.
Other objects and advantages will become evident to those skilled in the art from the following summary of my invention.